Applied Radiology

Breast cancer is the second most common form of cancer among women in the United States and the second leading cause of cancer death in women.

Yet there are new signs of hope. According to the American Cancer Society, “death rates from breast cancer have been declining since about 1990, with larger decreases in women younger than 50. These decreases are believed to be the result of earlier detection through screening and increased awareness, as well as improved treatment.”¹ Similarly, in Europe, 350,000 cases of breast cancer are diagnosed annually, yet nearly 90% of them may be cured if detected at an early stage. 

Behind these encouraging signs is the technology. Recent advances in mammography and breast tomosynthesis, along with emerging techniques in molecular imaging, are enabling physicians to detect smaller lesions at earlier stages in disease development.

The gold standard

Full-field digital mammography (FFDM) remains the gold standard in breast screening, yet the technology has its limitations, particularly in women with dense breasts, where overlapping tissue makes cancer detection more difficult and creates greater risks for that patient population. A study found that extensive mammographic density is strongly associated with the risk of breast cancer detected by screening or between screening tests.²

FFDM, however, is evolving and manufacturers continue to build on its capabilities. The MAMMOMAT Inspiration FFDM system by Siemens Healthcare, for example, provides screening, diagnostic, and stereotactic biopsy capabilities in a single system. To match breast density and thickness, the unit offers 3 anode/filter combinations.

Another concern is radiation exposure in FFDM, especially since exams are annual. Philips Healthcare’s MicroDose Mammography FFDM system combines a lower dose as compared to other FFDM solutions with a warm, padded, and breast-shaped contoured design for all around enhanced patient comfort.

An emerging technique within FFDM is contrast-enhanced spectral mammography (CESM) technology, which is used to assess the extent of breast cancers. In a study presented at RSNA 2011,³ researchers compared the diagnostic accuracy of CESM and MRI in assessing the extent of breast cancers. This preliminary study showed that CESM performs with good diagnostic accuracy with sensitivity slightly inferior to and specificity slightly superior to those of MRI.³

GE Healthcare’s newly FDA-cleared SenoBright system offers CESM technology. The system combines 2 high-quality images in the same orientation for each of the standard CC and MLO views. The first image exposure uses standard mammography parameters, while the second shows contrast-enhanced areas with the background tissue signal suppressed. The images together create a final view where signal from the normal tissue is removed and where contrast appears very distinctly. CESM may be useful as an adjunct exam to clarify equivocal lesions.

One system specifically designed for women with dense breasts is the somo•v Automated Breast Ultrasound (ABUS) system by U-Systems. ABUS is FDA-cleared for diagnostic use as an adjunct to mammography, but it is also scheduled for FDA premarket approval (PMA) review for a breast cancer screening indication. This would establish ABUS as an adjunctive screening breast ultrasound tool for women with dense breasts.

Tomosynthesis/3D mammography: A new dimension

One of the most anticipated developments in breast imaging has been the introduction of tomosynthesis, a 3-dimensional mammogram that takes multiple images of the breast. By adding a new dimension in breast cancer detection, tomosynthesis provides a clearer view through the overlapping structures of breast tissue, and may detect lesions missed by standard 2-dimensional mammograms.

Among the benefits of tomosynthesis: It improves radiologists’ ability to screen for and detect potential breast cancers; it helps to pinpoint the size, shape, and location of abnormalities; and it can help distinguish harmless abnormalities from malignancies, leading to fewer callbacks and less anxiety for women.⁴ In fact, a retrospective observer study compared the diagnostic performance of FFDM with that of digital breast tomosynthesis and found that tomosynthesis may result in a substantial decrease in recall rates.⁵

Hologic’s tomosynthesis solution is the Selenia Dimensions digital breast tomosynthesis system (Dimensions 3-D). Selenia Dimensions allows radiologists to offer their patients conventional 2-dimensional digital mammography and a 3-dimensional tomosynthesis exam in a single compression.

Other manufacturers have developed different approaches to 3-dimensional mammography. Providing a unique configuration to a 3-dimensional mammography system is the Giotto Image 3D and 3DL Digital Mammography Systems (3DL) by Giotto USA, which received FDA 510(k) clearance last November. The system has a ring-shaped, tilting gantry designed for easier, face-to-face patient positioning. The Giotto provides 2 systems in one by adding the optional biopsy digital stereotactic biopsy device, combining mammography and prone stereotactic biopsy all in one unit.

Fujifilm Medical Systems U.S.A offers its works-in-progress solution to 3-dimensional breast screening with 3D Digital Mammography. Pairs of stereo images of the breast are acquired and then viewed by combining a 3-dimensional review workstation and dedicated glasses designed to present 3-dimensional breast images.

To ease the adoption of new mammography techniques in clinical workflow, Sectra recently introduced its Breast Imaging PACS workstation, a solution that supports all imaging modalities, including breast tomosynthesis images. The breast images are automatically aligned and displayed side-by-side in the same size and dimension, a useful feature for combined 2-dimensional and tomosynthesis studies.

Molecular imaging clears some hurdles

Although screening mammography, especially when combined with ultrasound, has shown the ability to detect nonpalpable breast cancer, lesion detection in high-risk patients with dense breasts remains a serious obstacle. Yet molecular imaging may likely clear that hurdle. New studies show improved detection with techniques such as breast-specific gamma imaging (BSGI), also referred to as molecular breast imaging; positron emission mammography (PEM), and more recently, combination PET and MR imaging.

BSGI

The benefit of BSGI is it is less susceptible to breast density, since the radioactive tracer used in the procedure has a high affinity for metabolically active tumors. A study found BSGI had the highest overall sensitivity (91%) for breast cancer detection, significantly higher than that of mammography and ultrasound, 74% and 84% respectively.⁶

One system blazing a trail in BSGI is the Dilon 6800, a high-resolution, small field-of-view gamma camera. The system acquires images of the metabolic activity of breast lesions through radiotracer uptake.

Another recently available BSGI technology is the GE Discovery NM 750b scanner. The system features dual detectors with cadmium zinc telluride (CZT) technology for improved sensitivity and resolution.

PEM

An important emerging technology is positron emission mammography (PEM). Naviscan offers a high-resolution positron emission tomography (PET) scanner designed to provide a view of the location and the metabolic phase of a lesion in breast tissue, and assist doctors in distinguishing between benign and malignant lesions. In a study comparing PET to whole-body PET/CT of the breast, PEM had higher imaging sensitivity than PET/CT, particularly in small tumors. The results suggest PEM may be used to diagnose and characterize small lesions as a supplementary imaging modality for PET/CT.⁷

Combining PET/MRI for breast

Another striking development in breast imaging is combining MRI and PET images to acquire high-resolution anatomical and functional information. Fusing data can assist in detecting small lesions and assessing metastatic spread.

In an ongoing trial, researchers⁸ are comparing a prototype breast PET ring simultaneously with the Aurora Dedicated Breast MRI system to clinical PET on patients with suspected or biopsy-proven breast cancer. With the goal of evaluating the feasibility of simultaneous PET-MRI in the clinical setting, the researchers expect MRI with the breast scanner insert to deliver images with more precise and pinpoint resolution.

With these promising developments in breast imaging, there is hope that the second most common form of cancer among women will soon rank a lot lower.

References

1. Breast Cancer. American Cancer Society. http://www.cancer.org/Cancer/BreastCancer/DetailedGuide/breast-cancer-key-statistics. Last Revised: 01/06/2012. Accessed February 28, 2012.
2. Boyd FM, Guo H, Martin LJ, et al. Mammographic density and the risk and detection of breast cancer. N Engl J Med. 2007;356:227-236.
3. Dromain C, Canale S, Bidault F , et al. Value of contrast-enhanced spectral mammography (CESM) in women with newly diagnosed breast cancers compared to MRI: Preliminary results. Presented at: Radiological Society of North America 2011 Scientific Assembly and Annual Meeting; November 27- December 2, 2011 Chicago IL. rsna2011.rsna.org/search/event_display.cfm?printmode=n&em_id=11009315 Accessed March 2, 2012.
4. Massachusetts General Hospital. Imaging. 3D Mammography (Tomosynthesis). http://www.massgeneral.org/imaging/services/3D_mammography_tomosynthesis.aspx. Accessed March 2, 2012.
5. Gur D, Abrams G, Chough D, et al. Digital breast tomosynthesis: Observer performance study. AJR Am J Roentgenol. 2009;193: 586-591.
6. Weigert JM, Bertrand ML, Lanzkowsky L, et al. Results of a multicenter patient registry to determine the clinical impact of breast-specific gamma imaging, a molecular breast imaging technique. AJR Am J Roentgenol. 2012;198:W69–W75.
7. Eo JS, Chun IK, Paeng JC, et al. Imaging sensitivity of dedicated positron emission mammography in relation to tumor size. Breast. 2012;21:66-71. Epub 2011 Aug 25.
8. The collaborative effort is between Brookhaven National Laboratory, Upton, NY; Aurora Imaging Technology, Inc., North Andover, MA; Stony Brook University, Stony Brook, NY; and Taipei Medical University Hospital, Taipei, Taiwan. This work was also supported by the U.S. Department of Energy.